Signage indicating a reduction in the legal (e.g., posted) speed limit for an upcoming segment of roadway is common in certain parts of the world such as, for example, in the United States (US). Such a sign is referred to herein as a reduce speed ahead (RSA) sign. The intent of such a sign is to give a driver an advanced indication that they will need to reduce the speed of their vehicle to accommodate a speed limit (i.e., as indicated by a speed limit sign) of an approaching segment of the roadway that is less than a speed limit for a current segment of the roadway over which they are travelling. In this regard, RSA signs are beneficial with regard to roadway safety and to violations for speeding. However, it is also known that RSA signs are not used in many countries.
RSA signs have a variety of different visual implementations, depending on regulations/specifications of the country where such signs are located. As for usage, in location such as in the US, the signs are found on rural road when approaching an incorporated municipality from an unincorporated locality (i.e., approaching a more populated/busy area from a less populated/busy area). However, even in countries and municipalities where RSA signs are typically used, they are often not uniformly placed with respect to the following reduced speed zone, which can lead to drivers being surprised by a posted sign for a lower speed and having to decelerate uneconomically with respect to energy utilization/recover efficiency to avoid speeding. Furthermore, even with known computer vision technology used to read speed limit signs (sometimes referred to as traffic sign recognition (TSR)), it is possible to misclassify a RSA sign as a sign for a legal speed limit.
Therefore, implementation of functionality for notifying a driver of an approaching segment of roadway with a lower legal speed limit is beneficial, desirable, and useful.